What is the meaning of Dell Hymes when he said :"There are rules of use without which the rules of grammar will be useless"?Please as an essay if...

I won't write your essay, but I can give you my take on his ideas and appropriate background for support.

Dell Hymes, considered to be a "giant" of linguistics and anthropology, dedicated his life to the study of language, but not by studying the "abstract ways that people acquire grammar and other language skills" as other scholars in the field of his time. Instead, Dr. Hymes concerned himself with the basics of communication, rather than the intricacies of grammar study. Hs idea that "There are rules of use without which the rules of grammar will be useless" embraces the thought that language is dependent on more than grammar rules and structure.

In the world of linguistics, Hymes embraced the viewpoint of "communicative competence" which

involves knowing not only dictionary/grammar meaning, but also the rules that determine the appropriacy or otherwise of utterances in context.

Due to Hymes' claims, linguists began "turning their attention from language on the page to language between people" spending more time on communication rather than formal grammatical study.  In other words, linguists came to a realization that the study of grammar rules alone wasn't sufficient in terms of successful communication.  Hence, Hymes claim that "there are rules of use without which the rules of grammar will be useless' became the linguistic philosophy of his time.